Methodology

Distances are stored in metres and times in seconds. A mile is exactly 1.609344 kilometres. Results are converted to the units shown only at the last step, so changing units never changes the underlying value.

Values are rounded only for display: times to the nearest second, speeds to two decimals. Splits are computed from the unrounded pace, so they add up.

Pace calculators assume an even pace from start to finish. They do not model hills, heat, wind, fatigue or the start of a race. Treat the results as a planning aid.

When a result is faster than any world record pace, or slower than a relaxed walk, the calculator shows a warning. The warning never blocks the result; it only asks you to check what you entered.

Each calculation has automated tests for normal inputs, edge cases, invalid input and boundary values.